Heating apparatus for x-ray inspection

ABSTRACT

In a heating apparatus for X-ray inspection which heats at least one surface of a sample ( 7 ) by convection to perform an X-ray inspection, a planar heater  1  formed of an X-ray transmitting material having an opening  1   b  for passing gas is provided at a window part  22  for making an X-ray observation of the sample. Thereby, a board can be subjected to convection heating uniformly without enlarging or complicating the apparatus.

TECHNICAL FIELD

The present invention relates to a heating apparatus for X-rayinspection and, in particular, to a heating apparatus for X-rayinspection which is effectively used in analyzing a cause of defectivegeneration at a solder joint part and capable of heating an object to beexamined such as a sample to a target temperature or heating itaccording to a predetermined profile, thereby observing and recordingthe change in the state in real time.

BACKGROUND ART

In recent years, an assembled circuit board has been made high indensity, large in the number of layers and increasing in variety ofusing materials. Therefore, the necessity for an X-ray inspectioncapable of observing the interior or joint part of a component, inaddition to conventional optical inspections has increased.

In particular, an X-ray inspection at high temperature capable ofobserving a change in crystalline structure or a change in the meltedstate by heating a sample to high temperatures can be used to observe amelted state and behavior on cooling of a solder which exists at a jointpart of a component in real time. Therefore, this inspection is usefulin analyzing a cause of defective generation at a solder joint part.

Where an X-ray inspection is performed on a sample under heatingconditions, conventionally, there are often found cases that the sampleheated outside an inspection system is set inside the inspection systemand then subjected to observation. An X-ray inspection system having aheating apparatus is also proposed. However, at some of the heatingelements necessary in the heating apparatus or at a part of theapparatus, a metal low in X-ray transmission is used. Since the metalabsorbs, reflects, diffracts or scatters X-rays, a disadvantage is foundthat an X-ray receiving apparatus is unable to sufficiently receive anX-ray from an X-ray irradiation apparatus to result in a failure ofconducting an accurate inspection. Thus, a heating apparatus which iscapable of conducting a clear X-ray inspection under heating conditionshas been required.

Further, in order to conduct an accurate inspection, it is necessary toheat a sample to high temperatures as rapidly and uniformly as in actualproduction. Therefore, a heating apparatus which is capable ofperforming rapid and uniform heating has been required. Still further,since components have been downsized, there is a growing demand forobserving a very small component clearly at high magnification. In orderto reduce a focal length, a heating apparatus has been required to bemade thinner.

Thus, in Patent Document 1, an observation apparatus in which a heatercontaining a metal at some parts is separated from a sample piece toheat the sample with heated-air is proposed.

In Patent Document 2, a heating apparatus which uses ceramics formedinto a plate shape as a material constituting the heating apparatus isalso proposed.

In Patent Document 3, a reflow heating apparatus equipped with a heatingunit which heats compressed air and feeds it is still also proposed.

However, according to the above-described conventional technologies,there has been a problem that, where a sample heated outside aninspection system is set inside the inspection system and subjected toobservation, the sample decreases in temperature or unevenness intemperature distribution during the setting, thus resulting in a failureof controlling the temperature sufficiently. Further, there also hasbeen a problem that a change in the state of the sample in associationwith a change in the temperature, for example, void occurrence onmelting of solder or a change in a wet state, is unable to be observedaccurately and in real time according to a required profile.

Further, in an X-ray inspection system equipped with a heatingapparatus, a metal low in X-ray transmission is used at some of theheating elements of the heating apparatus or at a part of the apparatus.And, there also has been a problem that the metal blocks the field ofview for observing an X-ray image to result in a failure of making asufficient observation.

In order to cope with these problems, the observation apparatus known byPatent Document 1 is provided with a high-temperature chamber which hasa heater and a fan outside an observation path of a sample, therebyheating the sample by supplying heated-air from the high-temperaturechamber.

However, in the above-described method, it has been difficult to elevatethe temperature of a sample rapidly and also difficult to heat thesample in its entirety uniformly, thereby it has been difficult tocontrol the temperature of the sample, resulting in a failure of makingan observation in real time according to a required profile.

Further, the heating element is separated from the observation path,thereby an air sending passage and an air blowing mechanism ofheated-air is required. Therefore, a problem is posed that a system ismade larger to increase a focal length, by which it is impossible toobserve a very small component clearly at high magnification. There alsohave been problems that an angle for observation is limited, a system iscomplicated and fabricated with difficulty and the system is more likelyto malfunction.

In the heating apparatus known by Patent Document 2, ceramics formedinto a plate shape are used as a material constituting a heatingelement, thereby avoiding blockage of an X-ray by the materialconstituting the heating apparatus. However, a problem is posed that aceramics heater is slow in elevating temperatures, difficult incontrolling temperatures, easily broken and low in durability. Further,since the heating apparatus is not provided with a mechanism forgenerating air flow within it, there is found a problem that unevennessin temperature distribution inside the apparatus causes.

At present, reflow soldering heating methods used for boards producedworldwide are mostly done by convection heating. This is because, inmost cases, components are loaded above and below a glass epoxy board(the back surface is not flat) and therefore thermal conduction heatingis not usable.

However, there is a significant difference in soldering behavior betweenthermal conduction heating and convection heating which is actuallyconducted on the market. This is because there is a difference intemperature elevation speed between various parts such as a board, asolder paste and a component and also there is a difference in theamount of the solder paste to be dried and oxidized.

For this reason, an inspection which heats an assembled circuit board bythermal conduction heating that may cause a phenomenon which does nottake place in reality is meaningless in examining a mechanism of varioustypes of soldering defects caused by convection heating. The above factis known by technical experts of soldering as common knowledge.

Where a board is subjected to a motion image inspection with an X-ray,convection heating is needed for examining the soldering behavior whichtakes place in reality. However, conventional reflow heating furnacesfor X-ray inspection which have been so far filed are mostly conductedby thermal conduction heating.

In addition, convection heating is described in some of the patentapplications like that found in Patent Document 3. Since heated-air issupplied outside a field of view of an X-ray, the temperaturedistribution on a board is different from the actual temperaturedistribution and temperatures differ widely at various parts. Further,in the reflow heating apparatus known by Patent Document 3, heatedcompressed air is ejected to cause convection, thereby heating a sample.Therefore, a problem is posed that an air compressing mechanism isneeded to result in a larger and complicated apparatus.

PRIOR ART DOCUMENTS Patent Documents

-   [Patent Document 1] Japanese Published Unexamined Patent Application    No. 2005-227188-   [Patent Document 2] Japanese Published Unexamined Patent Application    No. Hei-9-138073-   [Patent Document 3] Japanese Published Unexamined Patent Application    No. 2009-123796

SUMMARY OF THE INVENTION

The present invention has been made in view of the problems found in theabove-described conventional technologies, and a first object of thepresent invention is to provide a heating apparatus for X-ray inspectioncapable of subjecting a board to uniform convection heating withoutenlarging or complicating the apparatus.

A second object of the present invention is to provide a heatingapparatus for X-ray inspection equipped with a heater which is low inprice, high in heat resistant temperature and long in service life.

In order to solve the above-described problems, the invention of claim 1is a heating apparatus for X-ray inspection which heats at least onesurface of a sample by convection to perform an X-ray inspectioncharacterized in that a planar heater formed of an X-ray transmittingmaterial having an opening for passing gas is provided at a window partfor making an X-ray observation of the sample.

The invention of claim 2 is the heating apparatus for X-ray inspectiondescribed in claim 1 in which the planar heater has a shape of a spiraltype, a zigzag type or a combination of the spiral type with the zigzagtype.

The invention of claim 3 is the heating apparatus for X-ray inspectiondescribed in claim 1 or claim 2 in which the planar heater is made of athin metal plate which can transmit X-rays.

The invention of claim 4 is the heating apparatus for X-ray inspectiondescribed in claim 3 in which the metal plate is reinforced with aninsulating plate where a heated-air blowing hole for smooth convectionis formed.

The invention of claim 5 is the heating apparatus for X-ray inspectiondescribed in claim 4 in which the heated-air blowing hole formed at theinsulating plate on the side of a sample is formed obliquely so as togenerate a swirling flow.

The invention of claim 6 is the heating apparatus for X-ray inspectiondescribed in claim 1 in which the planar heaters are disposed so as tooppose both surfaces of a sample, thereby making it possible to effectconvection heating from both surfaces of the sample.

The invention of claim 7 is the heating apparatus for X-ray inspectiondescribed in claim 1 in which a shielded heat isolation part formed ofan X-ray transmitting material having a gas supplying port is disposedon the planar heater so as to be overlapped.

The invention of claim 8 is the heating apparatus for X-ray inspectiondescribed in claim 1 in which a heated-air blowing plate formed of anX-ray transmitting material having a heated-air blowing hole for smoothconvection is disposed on the planar heater so as to be overlapped.

The invention of claim 9 is the heating apparatus for X-ray inspectiondescribed in claim 8 in which the heated-air blowing hole is providedobliquely.

The invention of claim 10 is the heating apparatus for X-ray inspectiondescribed in claim 7 in which the heating apparatus is constituted onrigid supporting bodies which oppose each other, the shielded heatisolation part and the planar heater are arranged on one of the windowpart and, of the shielded heat isolation part and the planar heater, atleast the shielded heat isolation part is arranged on the other of thewindow part.

The invention of claim 11 is the heating apparatus for X-ray inspectiondescribed in claim 10 in which the heating apparatus is provided with agas supplying pipe exclusively for cooling on the supporting bodies.

The invention of claim 12 is the heating apparatus for X-ray inspectiondescribed in claim 10 or claim 11 in which the heating apparatus isprovided with an exhaust opening on the supporting bodies.

The invention of claim 13 is the heating apparatus for X-ray inspectiondescribed in any one of claim 10 to claim 12 in which the heatingapparatus is provided with a limit switch between rigid supportingbodies which oppose each other.

The invention of claim 14 is the heating apparatus for X-ray inspectiondescribed in any one of claim 10 to claim 13 in which a pressure sensoris disposed on a gas supplying pipe connected to a gas supplying port ofthe shielded heat isolation part.

The invention of claim 15 is the heating apparatus for X-ray inspectiondescribed in claim 6 or claim 8 in which at least the shielded heatisolation part and the planar heater are made available as modules.

The invention of claim 16 is the heating apparatus for X-ray inspectiondescribed in any one of claim 1 to claim 15 in which the heatingapparatus is a reflow furnace.

The invention of claim 17 is a heating apparatus for X-ray inspectionwhich is provided with a planar heater made of a thin metal plate thatcan transmit X-rays.

According to the heating apparatus for X-ray inspection described inclaim 1, heating is done by using gas which has passed into an openingformed on the planar heater, thus making it possible to promoteconvection and also finely control temperatures. Further, an atmosphereinside the heating apparatus can be controlled, by which it is possibleto prevent or control combustion and oxidation and also make anobservation under a specific gaseous atmosphere.

According to the heating apparatus for X-ray inspection described inclaim 2, the shape of the planar heater is formed into a zigzag type, aspiral type or a combination of the zigzag type with the spiral type, bywhich it is possible to control a value of electric current flowingthrough the heating element and voltage freely and easily. Thereby, itis possible to establish the performance, specification and standard ofthe heating apparatus freely and easily.

According to the heating apparatus for X-ray inspection described inclaim 3, the planar heater can be produced at a very low cost and isalso made high in heat resistant temperature and long in service life.

According to the heating apparatus for X-ray inspection described inclaim 4, the planar heater can be constituted with an extremely thinmetal plate.

According to the heating apparatus for X-ray inspection described inclaim 5, the heated-air blowing hole is provided obliquely, thus makingit possible to generate a swirling flow inside a sample chamber andprovide heating rapidly and uniformly.

According to the heating apparatus for X-ray inspection described inclaim 6, it is possible to provide convection heating from both surfacesof a sample.

According to the heating apparatus for X-ray inspection described inclaim 7, the shielded heat isolation part and the planar heater arrangedso as to be overlapped can be constituted with a material favorable inX-ray transmission properties at the window part for making an X-rayinspection of a sample. Thereby, it is possible to provide a heatingapparatus capable of making a clear observation under heating conditionsat a free angle by using an X-ray inspection system easily.

According to the heating apparatus for X-ray inspection described inclaim 8, the planar heater and the heated-air blowing plate having theheated-air blowing hole for smooth convection are arranged so as to beoverlapped. Thereby, the heating apparatus can be downsized and also aheating part can be easily made closer to a sample. Further, heated-airwhich has been heated by the planar heater is directly ejected throughthe heated-air blowing hole formed on the heated-air blowing plate.Thereby, it is possible to feed heated-air which is sufficient intemperature and wind velocity without using a blower or a pressuremechanism and without lowering temperatures on a flow path. Therefore,convection heating due to the heated-air is used to elevate thetemperature of the sample rapidly and the sample in its entirety can beheated uniformly. As a result, it is possible to easily control thetemperature of the sample and also make an observation in real timeaccording to a required profile.

Use of the above-described heating system makes it possible to downsizean apparatus and bring a sample closer to an X-ray inspection system.Therefore, it is possible to observe a very small component clearly athigh magnification.

Further, supply of gas makes it possible to control an atmosphere insidethe heating apparatus. Therefore, it is possible to prevent or controlcombustion and oxidation and make an observation in a specific gaseousatmosphere.

According to the heating apparatus for X-ray inspection described inclaim 9, the heated-air blowing hole is provided obliquely, therebymaking it possible to generate a swirling flow inside the sample chamberand effect rapid and uniform heating.

According to the heating apparatus for X-ray inspection described inclaim 10, the apparatus is constituted on rigid supporting bodies whichoppose each other, the shielded heat isolation part and the planarheater are arranged on one surface of the window part and, of theshielded heat isolation part and the planar heater, at least theshielded heat isolation part is arranged on the other surface of thewindow part. Thereby, a sample can be heated by selecting variousheating methods, for example, convection heating from both surfaces ofthe sample, convection heating from one surface and thermal conductionheating from the other surface, and convection heating from one surfaceand no heating from the other surface. Thus, it is possible to provideheating according to a state of the sample.

According to the heating apparatus for X-ray inspection described inclaim 11, the gas supplying pipe exclusively for cooling is provided onthe supporting bodies. Thereby, it is possible to provide rapid coolingor control a cooling state. It is also possible to observe not only theinfluence of heating but also the influence of cooling.

According to the heating apparatus for X-ray inspection described inclaim 12, the exhaust opening is provided on the supporting bodies, thusmaking it possible to control temperatures inside the sample chamber andalso a gaseous atmosphere easily.

According to the heating apparatus for X-ray inspection described inclaim 13, the limit switch is provided between the rigid supportingbodies, thus making it possible to prevent heating in an open state andprovide a heating apparatus high in safety.

According to the heating apparatus for X-ray inspection described inclaim 14, the pressure sensor is disposed on the gas supplying pipeconnected to the gas supplying port at the shielded heat isolation part.Thereby, it is possible to prevent heating without gas supply andprovide a heating apparatus free of risk of overheating and high insafety.

According to the heating apparatus for X-ray inspection described inclaim 15, at least the shielded heat isolation part and the planarheater are made available as modules, thus making it possible to providea heating apparatus excellent in maintenance properties and costperformance.

According to the heating apparatus for X-ray inspection described inclaim 16, the heating apparatus for X-ray inspection is a reflowfurnace, by which it is possible to provide a reflow furnace capable ofmaking an X-ray inspection of a board and also easy in controllingtemperatures.

According to the heating apparatus for X-ray inspection described inclaim 17, the planar heater made of a thin metal plate that can transmitX-rays is provided, thus making it possible to provide a heatingapparatus for X-ray inspection having a heater low in cost, high in heatresistant temperature and long in service life.

On the basis of the above description, working effects of the heatingapparatus according to the invention as claimed in the applicationconcerned are listed hereinafter.

A first effect is that an X-ray inspection system under heatingconditions can be used to observe a sample clearly.

A second effect is that a sample can be heated rapidly.

A third effect is that a sample can be heated uniformly.

A fourth effect is that a sample can be heated at high temperatures.

A fifth effect is that a method for heating a sample can be selected.

A sixth effect is that a sample can be controlled for cooling.

A seventh effect is that a sample can be observed in real time.

An eighth effect is that a sample can be observed at an angle that canbe established freely.

A ninth effect is that the apparatus can be made thin.

A tenth effect is that the apparatus can be made simple.

A eleventh effect is that the apparatus is high in durability.

A twelfth effect is that the apparatus can be operated safely.

A thirteenth effect is that the apparatus is high in maintenanceproperties.

A fourteenth effect is that the apparatus is excellent in costperformance.

Further, as a matter of common knowledge, it was thought impossible inview of X-ray transmission to use a metal plate large in atomic weightas a heater. X-ray transmission properties of a metal can be simplyexpressed in a manner that the transmission properties are lower as thevalue obtained by multiplying an atomic number with the thickness islarger. As a realistic problem, a 30 μm-thick stainless steel plate ofSUS 430 was processed into a spiral type and used as a heaterexperimentally. This heater was excellent and free of any problems withrespect to X-ray transmission properties, sufficient in heating valueand found to be long in service life. The plate is made thinner toenhance the X-ray transmission properties and increase the electricresistance and therefore can be used as a heater. Further, this heateris extremely low in cost and can be processed by etching or others andalso high in heat resistant temperature and long in service life.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view which shows an entire constitution ofEmbodiment 1 of a heating apparatus for X-ray inspection according tothe present invention.

FIG. 2 is a plan view which shows the shape of a planar heater used inEmbodiment 1.

FIG. 3 is also an exploded perspective view of the planar heater.

FIG. 4 is a plan view which shows the shape of another example of theplanar heater.

FIG. 5 is also a plan view which shows the shape of still anotherexample.

FIG. 6 is also a plan view which shows the shape of a further example.

FIG. 7 is also a plan view which shows the shape of a still furtherexample.

FIG. 8 is also a perspective view which shows the shape of anothersample.

FIG. 9 is a cross sectional view which shows an entire constitution ofEmbodiment 2 of the heating apparatus for X-ray inspection according tothe present invention.

FIG. 10 is a cross sectional view which shows an entire constitution ofEmbodiment 3 of the heating apparatus for X-ray inspection according tothe present invention.

FIG. 11 is a cross sectional view which shows important constitution ofEmbodiment 3.

FIG. 12 is a plan view which shows a constitution of a heated-airblowing plate used in Embodiment 3.

FIG. 13 is also a cross sectional view which shows an arrangement ofheated-air blowing holes in Embodiment 3.

FIG. 14 is a cross sectional view which shows an entire constitution ofEmbodiment 4 of the heating apparatus for X-ray inspection according tothe present invention.

FIG. 15 is also a cross sectional view which shows an entireconstitution of Embodiment 5.

FIG. 16 is also a perspective view which shows one example of amechanism which allows supporting bodies to oppose each other.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a detailed explanation will be made for embodiments of thepresent invention by referring to drawings.

FIG. 1 is a cross sectional view which shows an entire constitution ofthe heating apparatus for X-ray inspection according to the presentinvention. In this figure, the reference number 1 depicts a planarheater; 2, copper plate electrode; 3, screw; 4, crimp-type terminal; 5,covered conductor line; 6, insulating plate high in heat resistance andheat conductivity; 7, print circuit board; 8, electronic componentsoldered such as a semiconductor chip to be soldered, for example; 9,copper land; 10, solder paste; 13, sealant; 14, shielded heat isolationpart; 15, gas supplying pipe; 20, X-ray generating part of X-rayirradiation apparatus; 21, X-ray irradiation range; and 23, X-rayreceiving apparatus.

The planar heater 1 is constituted with, for example, a 30 μm-thick thinstainless steel plate 1 a (for example, SUS430). As shown in FIG. 2, theplanar heater is given an electric resistance value suitable for aheater and provided with a slit 1 b for allowing gas to pass.

Since the metal plate is extremely low in electric resistance, there isa case where a large current may flow even at a low voltage. However,adoption of a thin-plate formed in a spiral shape makes it possible toeasily control electric resistance and a value of electric current. Apower supply and a cable for general purpose can be used to yield a highheating value.

In addition, the heater 1 a made of a metal plate is thin in thicknessand therefore unable to keep the plate shape. Thus, as shown in FIG. 3(for easy understanding, the top and the bottom are illustratedreversely unlike the case of FIG. 1), a sandwich structure is providedthat, for example, 1 mm-thick insulating plates (for example, those madeof boron nitride BN, ceramics and mica) 1 c, 1 e are used to hold theheater 1 a therebetween from both surfaces. In this instance, at a sitewhich is overlapped on the slit 1 b of the heater 1 a at the insulatingplate 1 c on the side of a gaseous space (below in FIG. 3), many gasholes 1 d perpendicular to the surface of the insulating plate 1 c areformed. At a site which is overlapped on the slit 1 b of the heater 1 aat the insulating plate 1 e on the side of a sample (above in FIG. 3),many gas holes 1 f oblique to the surface of the insulating plate 1 e soas to generate a swirling flow are formed, such as the heated-airblowing holes 32 a illustrated in FIG. 13 to be described later.

In addition, there is no particular restriction on the size and shape ofthe planar heater 1 or the structure, size and shape of the spiral type.Patterns of the spiral type and the zigzag type can be provided invarious ways as shown in plan views of FIG. 4 to FIG. 7. There is noparticular restriction on the patterns in addition to those shown inthese figures. Where the slit 1 b is narrow in width to result ininsufficient gas supply, gas holes 1 b′ may be provided as shown in FIG.8.

The metal plate heater 1 a can be formed as a metal-resistant thin filmon an insulating plate such as ceramics by vapor deposition of PVD, CVDor others, in addition to etching. It is desirable that a target towhich the metal plate heater 1 a is deposited is an insulating plate 1 eon the side of a sample where oblique gas holes 1 f are formed. In thisinstance, it is also possible to omit an insulating plate 1 c on theside of the gaseous space.

A material of the metal plate is not restricted to an alloy of Fe—Crsuch SUS 430 or other stainless steel. Other metals which can be formedinto a thin film and which are heat resistant, free of deterioration dueto oxidation and give resistivity usable as a heater may include alloysof Ni—Cr, Ni—Cr—Fe, Fe—Cr—Al, Cu—Mn, Cu—Ni and other metals.

In the above-constituted Embodiment 1 of the present invention, in orderto activate the heating apparatus, at first, voltage is applied to acovered conductor line 5. Although it is acceptable that the appliedvoltage may be direct current or alternative current, the current willflow via the crimp-type terminal 4 into the copper plate electrode 2.

Further, since the planar heater 1 is firmly attached to the copperplate electrode 2 with the screw 3, the current will flow uniformlyinside the planar heater 1. In this instance, the metal plate is low inelectric resistance and easily electrified, by which the current flowseasily to produce a heating value according to electric power.

Since heating is generated uniformly and also the metal plate in itselfis high in heat conductivity, the planar heater 1 undergoes rapid anduniform temperature elevation.

A print circuit board 7, which is a sample, is installed on the planarheater 1 via an insulator 6 high in heat resistance and heatconductivity. The insulator 6 favorably includes a plate and a sheetmade of alumina ceramics, polyimide resin, silicone resin, fluorocarbonresin and mica, with no particular restriction thereon. A material canbe selected freely depending on a required temperature. Further, theplanar heater 1 may be covered with the insulator 6.

The sample can be installed directly on the planar heater 1 only via theinsulator 6 high in heat resistance and heat conductivity. Therefore,the sample can also be rapidly and uniformly heated in association witha rapid and uniform temperature elevation of the planar heater 1.

Further, the heating value can be easily controlled by controlling thevoltage while being monitored with a thermoelectric couple. It is,thereby, possible to control temperatures of the sample according to arequired profile.

In association with temperature elevation of the planar heater 1, theprint circuit board 7, which is a sample installed on the insulator 6,undergoes rapid and uniform temperature elevation within the plane. Astainless steel plate of the present embodiment is high in heatresistant temperature and able to sufficiently fuse a solder paste 10.In association with temperature elevation, the solder paste 10 is meltedto wet an electronic component 8 and a copper land 9 and join them.

Further, an observation can be made in real time in a predeterminedtemperature profile, which is helpful in clarifying a void developingmechanism.

Still further, since no heat transmitting mechanism is needed outside afield of view for inspection, there is no restriction on an observationangle. Therefore, an apparatus can be made thin and simplified and alsoproduced easily. The metal plate in itself is also superior in strength,thus making it possible to easily obtain a highly durable heatingapparatus.

In addition, in FIG. 1 and FIG. 2, the planar heater 1 is formed in aflat plate shape. This plate may be made round or bent, thereby makingit possible to provide a cylindrical or rectangular tubular heatingapparatus as described in Patent Document 2, for example.

The present embodiment is characterized in that the metal plate isdirectly electrified to generate heating. However, in addition to themetal plate, a planar heater which is constituted with a carbon-fiberreinforced carbon composite material plate formed of an advancedcomposite material made of a carbon fiber and a carbon matrix, forexample, may be used. In this instance, those which meet the followingthree characteristics are all included in carbon-fiber reinforced carboncomposite materials. In other words, a first characteristic is thatthere are no serious disadvantages such as oxidation and deteriorationeven on heating at 250° C. in the atmosphere, a second characteristic isthat electric conductivity is found, and a third characteristic is thatcarbon fiber is contained at least partially in the material.

In addition, here, a carbon-fiber reinforced carbon composite materialis to have a heat resistant temperature of 250° C. or higher. However,the carbon-fiber reinforced carbon composite material is high in heatresistance and can be heated up to a high temperature of 1000° C. orhigher, if necessary. By temperature control or gas atmosphere controlor forming an oxidation preventing film, an observation can be madeeasily under high temperature conditions. In addition to theabove-described electronic component, various materials and componentscan be observed for the heating behavior.

Further, a carbon-fiber reinforced carbon composite material plate canbe used as a sealing wall material of the present heating apparatus.Thereby, it is possible to easily obtain a heating apparatus which islight in weight, high in heat resistance, small in size, simple inconstitution and high in durability.

In the present embodiment, gas which has been supplied through the gassupplying pipe 15 is allowed to pass into the slit 1 b provided on theplanar heater 1 and heated, by which atmosphere heating due toconvection is added to heating due to contact and irradiation, thusmaking it possible to finely control temperatures elaborately. Not onlycan the speed of temperature elevation be controlled by the flow rate ofthe gas but also cycle operation can be conducted between temperatureelevation and cooling. Further, there are advantages that oxidation andcombustion can be prevented or controlled by injecting an inert gas andothers, an observation can be made under a specific gas atmosphere, anda poisonous gas generated from a sample can be discharged outside toprevent adverse effects on the sample and an apparatus. Still further,after completion of observation, ambient air or cold air can be sent tocool the sample and the apparatus rapidly.

FIG. 9 shows Embodiment 2 of the heating apparatus in which the planarheaters 1 shown in FIG. 2 and FIG. 3 are installed above and below. Inthe figure, the reference number 16 depicts an insulation spacerinserted between the lower planar heater 1 and the print circuit board7.

According to the present embodiment, it is possible to conduct smoothheating by convection from above and below.

Next, a detailed explanation will be made for Embodiment 3 of thepresent invention which is a further improvement of Embodiment 2.

FIG. 10 is a cross sectional view for explaining Embodiment 3. In thisfigure, the reference number 22 depicts a window part; 32, heated-airblowing plate; 32 a, heated-air blowing hole; 27, sample chamber; and31, supporting body. Further, the gas supplying pipe 15 can be used bybeing fitted into heated-air blowing holes 14 a on the shielded heatisolation part 14 at the heating part shown in the cross sectional viewof FIG. 11. In this figure, the reference number 31 a is an exhaustopening formed, for example, on a side surface of the supporting body31. Since as for the other points, the present embodiment is similar toEmbodiment 2, the same reference numbers are used to omit anexplanation.

In the above-constituted Embodiment 3, in order to heat a sample,voltage is applied to the planar heater 1, with gas being supplied fromthe gas supplying pipe 15. The voltage may be applied from a partoutside the window part 22 at the end of the planar heater 1. Further,the voltage can be applied either by direct current or alternativecurrent. In addition, on observation, a thermoelectric couple can beinstalled at a part which gives no trouble in making an X-rayobservation, thereby monitoring temperatures.

Further, in the figure, the heating apparatus is installed horizontallybut can be installed vertically or obliquely when necessary. Variouscombination of methods for installing the heating apparatus with methodsfor setting a sample, makes it possible to observe the sample at anyangle.

With an increase in temperature of the planar heater 1, gas suppliedfrom the gas supplying pipe 15 is elevated in temperature, by whichheated-air is blown from the heated-air blowing holes 32 a to generate aheated swirling flow inside the sample chamber 27 and elevate thetemperature inside the sample chamber 27. Then, the print circuit board7, which is a sample, is also elevated in temperature rapidly anduniformly inside the plane, and the solder paste 10 is melted to wet theelectronic component 8 and the copper land 9 and join them.

In the heating apparatus of the present invention, since only a materialexcellent in X-ray transmission properties is used at the window part 22which is an X-ray observation range of a sample, it is possible toobserve the wetting behavior of solder clearly under various temperatureconditions.

Further, a real-time observation can be made in a predeterminedtemperature profile, which is helpful in clarifying a void developingmechanism.

Still further, since no heat transmitting mechanism from outside isneeded, it is possible to downsize and make thinner an apparatus.Therefore, it is possible to bring a sample closer to an X-rayinspection system and observe a very small component clearly at highmagnification.

The heated-air blowing holes 32 a are provided minutely in a largenumber as shown in the plan view of FIG. 12, thus making it possible toincrease the blowing speed of heated-air. Further, the heated-airblowing holes 32 a are located so as to be in agreement with a clearanceof the planar heater 1 and can be provided freely according to the shapeof the planar heater 1, with no particular restriction on thearrangement thereof. Still further, the heated-air blowing holes areprovided obliquely, thereby generating a swirling flow without using amechanism such as a fan to make temperatures uniform more simply. Inaddition, a way of providing the blowing holes can be set in variousdirections as shown in the cross sectional views of FIGS. 13 (a), (b)and (c). There is no particular restriction on the directions, inaddition to those shown in the figure.

Although there is no particular restriction on the number of gassupplying pipes 15, two or more gas supplying pipes may be provided,thereby making it possible to eliminate an unevenness in gas flow andalso attain a uniform temperature. The flow rate of gas can also bereferred to control the speed of temperature elevation. Further, gassupplied from the gas supplying pipe 15 may by selected, by which it ispossible to make an observation under a specific gas atmosphere and alsoprevent or control oxidation and combustion by injecting an inert gas orothers. Still further, the gas supplying pipe 15 may be constituted witha material excellent in X-ray transmission properties, by which thesupply of gas can be controlled, with the X-ray transmission propertieskept.

Further, on cooling, a coolant gas is allowed to flow through the gassupplying pipe 15. And, a gas supplying pipe exclusively for cooling isprovided on the supporting bodies 31, thus making it possible to controlcooling rapidly. Thereby, it becomes possible to control rapid coolingand a state of cooling, by which it is possible to observe coolingeffects on various phenomena such as a liftoff phenomenon and alsoconduct a cycle operation between temperature elevation and cooling.

In addition, an exhaust opening 31 a may be provided on the supportingbody 31 of the heating apparatus, thus making it possible to control thegas atmosphere and flow rate and also control temperatures easily.Further, it is possible to provide a heating apparatus capable ofdischarging quickly a poisonous gas generated from a sample on heatingand high in safety.

In the present embodiment, the planar heater 1 constituted with amaterial excellent in X-ray transmission properties is used. The planarheater 1 is made of carbon in particular, thereby providing a heatercapable of transmitting X-rays and also easily attaining uniformtemperature elevation by electrification. In addition, when carbon isused as a material, carbon fibers may be formed into a plane shape andused. Further, where carbon is in particular a carbon-fiber reinforcedcarbon composite material, electricity will flow easily to generate aheating value according to electric power due to the small electricresistance and easy electrification. This heating is uniform and acarbon-fiber reinforced carbon composite material plate itself is alsohigh in heat conductivity, thus making it possible to elevate thetemperature of the planar heater 1 rapidly and uniformly.

Further, an oxidation preventing film may be provided on the surface ofcarbon, thus making it possible to prevent the oxidation anddeterioration of carbon and also improve the durability. Materials ofthe oxidation preventing film include oxidation preventing films made oftitanium diboride and silicon carbide, with no restriction thereon.

The present embodiment is characterized in that a material of theshielded heat isolation part 14 and that of the heated-air blowing plate32 are any one of ceramics, heat resistant resin, heat resistant rubber,glass, glass fiber, mica and insulation-treated carbon or a combinationthereof. These materials are favorable in X-ray transmission propertiesand also excellent in durability, heat resistance and insulatingproperties and, therefore, used favorably. More specifically, a plateand a sheet made of alumina ceramics, polyimide resin, silicone resin,fluorocarbon resin, glass, glass fiber, mica or insulation-treatedcarbon are favorably used. In addition to these materials, the materialscan be selected freely depending on a required temperature and strength,with no particular restriction thereon. Further, carbon can be subjectedto insulation treatment by various methods such as coating with aninsulating material and doping into an insulating agent, with noparticular restriction thereon.

The present embodiment is also characterized in that a material of thegas supplying pipe 15 and that of a jig for fixing the shielded heatisolation part 14, the gas supplying pipe 15 or the heated-air blowingplate 32 are any one of ceramics, heat-resistant resin, heat-resistantrubber or a combination thereof. These materials are favorable in X-raytransmission properties and also excellent in durability, heatresistance and insulating properties and, therefore, can be usedfavorably. More specifically, in addition to these materials, aluminaceramics, polyimide resin, silicone resin and fluorocarbon resin arefavorably used, with no particular restriction thereon. The materialscan be selected freely depending on a required temperature and strength.

The present embodiment is characterized in that it is constituted onrigid supporting bodies 31 which oppose each other, the shielded heatisolation part 14, the planar heater 1 and the heated-air blowing plate32 are arranged at one of the window part 22 and, of the shielded heatisolation part 14, the planar heater 1 and the heated-air blowing plate32, at least the shielded heat isolation part 14 is arranged at theother of the window part 22. Thereby, a sample can be heated byselecting a heating method depending on types of the sample, forexample, convection heating from both surfaces of the sample as shown inthe cross sectional view of FIG. 9, convection heating from one surface(the upper surface in the figure) and thermal conduction heating fromthe other surface (the lower surface in the figure) as described inEmbodiment 3 shown in the cross sectional view of FIG. 14, andconvection heating from one surface (the upper surface in the figure)and no heating from the other surface (the lower surface in the figure)as described in Embodiment 4 shown in the cross sectional view of FIG.15. Thus, it is possible to provide heating according to a state of thesample.

As for a mechanism for allowing the supporting bodies 31 to oppose eachother, the supporting bodies 31 can be joined by using a hinge as shownin the perspective view of FIG. 16 so as to be opened and closed.Alternatively, the supporting bodies 31 are allowed to be fitted into orto slide, with no particular restriction on the mechanism.

Further, a limit switch 40 may be installed between the supportingbodies 31, thus making it possible to conduct heating only when thesupporting bodies 31 are closed. Therefore, it is possible to prevent anaccident. In this instance, since the side of a lid is slightly widenedlaterally from the side of the main body to install the limit switch 40outside, the limit switch 40 is less likely to be influenced by hightemperatures inside and also the lid can be closed securely.

Still further, as shown in FIG. 1, a pressure sensor 42 may be disposedon the gas supplying pipe 15, thus making it possible to conduct heatingonly when gas is supplied. Thus, it is possible to prevent an accidentsuch as overheating of the heating apparatus.

In addition, the limit switch 40 and the pressure sensor 42 are requiredto be provided outside the range of the window part 22.

In the heating apparatus of the present invention, among constitutingcomponents, the planar heater 1, the shielded heat isolation part 14 andthe heated-air blowing plate 32 are repeatedly subjected to heat cycleand therefore expected to be deteriorated earlier than other components.In particular, where carbon is used as a material constituting theplanar heater 1, there is a concern that the planar heater 1 may bedeteriorated due to oxidation at a high temperature. Thus, the planarheater 1, the shielded heat isolation part 14, and the heated-airblowing plate 32 provided when necessary may be made available asmodules, thereby only worn parts can be exchanged to improve themaintenance and cost performance.

The heating apparatus of the present embodiment is characterized asbeing a reflow furnace. Thereby, it is possible to provide a reflowfurnace capable of examining a board with an X-ray and easilycontrolling temperatures.

Embodiment 1

Planar heaters made of a carbon-fiber reinforced carbon compositematerial plate were disposed above and below and formed into the shapeshown in FIG. 1. Then, they were used to fabricate a heating apparatus.

Embodiment 2

Planar heaters made of a carbon-fiber reinforced carbon compositematerial plate were disposed above and below and formed into the shapeshown in FIG. 9. Then, they were used to fabricate a heating apparatus.

Embodiment 3

Planar heaters made of a carbon-fiber reinforced carbon compositematerial plate and ceramics plates were used to fabricate the heatingapparatus shown in FIG. 10 and FIG. 16.

Embodiment 4

Planar heaters made of a carbon-fiber reinforced carbon compositematerial plate and ceramics plates were used to fabricate the heatingapparatus shown in FIG. 14 and FIG. 16.

Embodiment 5

A planar heater made of a carbon-fiber reinforced carbon compositematerial plate and a ceramics plate were used to fabricate the heatingapparatus shown in FIG. 15 and FIG. 16.

Embodiment 6

Heaters made of carbon fiber and processed into a plane shape andceramics plates were used to fabricate the heating apparatus shown inFIG. 10 and FIG. 16.

Comparative Example 1

A ceramics heater was used to fabricate a heating apparatus.

Comparative Example 2

A sheathed heater having a nichrome wire as a heating source and ablower fan were used to fabricate a heating apparatus.

Any one of the heating apparatuses shown in Embodiments 1 to 6 underwentrapid and uniform temperature elevation according to a predeterminedprofile. Further, an X-ray observation was able to be made in real timefor a motion image in which solder in a melted state vibrated under aceramics condenser component and jumped out immediately beforesolidification. The heating apparatus of Comparative example 1 was slowin temperature elevation and unable to effect temperature elevationaccording to a predetermined profile. The heating apparatus ofComparative example 2 was also slow in temperature elevation, unable toeffect temperature elevation according to a predetermined profile andalso unable to heat a sample to a required temperature.

INDUSTRIAL APPLICABILITY

The heating apparatus for X-ray inspection is useful in analyzing acause of defective generation at a solder joint part in particular andable to heat an object to be examined such as a sample to a targettemperature or heat it according to a predetermined profile, therebyobserving and recording the change in the state in real time.

DESCRIPTION OF REFERENCE NUMBERS

-   1: Planar heater-   1 a: Metal plate heater-   1 b: Slit-   1 c, 1 e: Insulating plate-   1 d, 1 f: Gas holes-   6: Insulating plate-   7: Print circuit board-   8: Electronic component-   9: Copper land-   10: Solder paste-   14: Shielded heat isolation part-   15: Gas supplying pipe-   20: X-ray generating part-   21: X-ray irradiation range-   22: Window part-   23: X-ray receiving apparatus-   27: Sample chamber-   31: Supporting body-   31 a: Exhaust opening-   32: Heated-air blowing plate-   32 a: Heated-air blowing hole-   40: Limit switch-   42: Pressure sensor

1. A heating apparatus for X-ray inspection which heats at least onesurface of a sample by convection to perform an X-ray inspection,comprising, a planar heater provided at a window part for making anX-ray observation of the sample, the planer heater comprising a thinmetal plate which can transmit X-rays having a shape of a spiral type, azigzag type or a combination of the spiral type with the zigzag type orhaving holes and electric insulating plate integrated with the thinmetal plate, the integrated electric insulating plate and the thin metalplate has heated-air blowing holes at least a part thereof communicatedwith each other.
 2. (canceled)
 3. (canceled)
 4. (canceled)
 5. Theheating apparatus for X-ray inspection according to claim 1, wherein theheated-air blowing hole formed at the electric insulating plate on theside of a sample is formed obliquely so as to generate a swirling flow.6. The heating apparatus for X-ray inspection according to claim 1,wherein the planar heaters are disposed so as to oppose both surfaces ofthe sample, thus making it possible to effect convection heating fromthe both surfaces of the sample.
 7. The heating apparatus for X-rayinspection according to claim 1, wherein a shielded heat isolation partformed of an X-ray transmitting material having a gas supplying port isdisposed on the planar heater so as to be overlapped.
 8. The heatingapparatus for X-ray inspection according to claim 1, wherein aheated-air blowing plate formed of an X-ray transmitting material havinga heated-air blowing hole for smooth convection is disposed on theplanar heater so as to be overlapped.
 9. The heating apparatus for X-rayinspection according to claim 8, wherein the heated-air blowing hole isprovided obliquely.
 10. The heating apparatus for X-ray inspectionaccording to claim 7, wherein the heating apparatus is disposed on rigidsupporting bodies which oppose each other, the shielded heat isolationpart and the planar heater are arranged on one of the window part and,of the shielded heat isolation part and the planar heater, at least theshielded heat isolation part is arranged on the other of the windowpart.
 11. The heating apparatus for X-ray inspection according to claim10, wherein the heating apparatus is provided with a gas supplying pipeexclusively for cooling on the supporting bodies.
 12. The heatingapparatus for X-ray inspection according to claim 10, wherein theheating apparatus is provided with an exhaust opening on the supportingbodies.
 13. The heating apparatus for X-ray inspection according toclaim 10, wherein the heating apparatus is provided with a limit switchbetween rigid supporting bodies which oppose each other.
 14. The heatingapparatus for X-ray inspection according to claim 10, wherein a pressuresensor is disposed on a gas supplying pipe connected to a gas supplyingport of the shielded heat isolation part.
 15. The heating apparatus forX-ray inspection according to claim 6, wherein at least the shieldedheat isolation part and the planar heater are made available as modules.16. The heating apparatus for X-ray inspection according to claim 1,wherein the heating apparatus is a reflow furnace.
 17. (canceled)